Background The biodiversity of the mycobiota of soft cheese rinds such as Brie or Camembert has been extensively studied, but scant information is available on the fungi colonizing the rinds of cheese produced in the Southern Switzerland Alps. This study aimed at exploring the fungal communities present on rinds of cheese matured in five cellars in Southern Switzerland and to evaluate their composition with regards to temperature, relative humidity, type of cheese, as well as microenvironmental and geographic factors. We used macro- and microscopical morphology, matrix-assisted laser desorption/ionization–time of flight (MALDI-TOF) mass spectrometry, and sequencing to characterize the fungal communities of the cheeses, and compared them with metabarcoding targeting the ITS region. Results Isolation by serial dilution yielded 201 isolates (39 yeasts and 162 filamentous fungi) belonging to 9 fungal species. Mucor and Penicillium were dominant, with Mucor racemosus, M. lanceolatus, P. biforme, and P. chrysogenum/rubens being the most frequent species. All but two yeast isolates were identified as Debaryomyces hansenii. Metabarcoding detected 80 fungal species. Culture work and metabarcoding produced comparable results in terms of similarity of the fungal cheese rind communities in the five cellars. Conclusions Our study has shown that the mycobiota on the rinds of the cheeses studied is a comparatively species-poor community influenced by temperature, relative humidity, type of cheese, and manufacturing steps, as well as microenvironmental and possibly geographic factors.
Background: The fungal biodiversity on cheese rinds has been extensively studied for some soft cheeses such as Brie, Camembert, and Roquefort, but scant information is available on the microbiota colonizing the rinds of cheese produced in the Southern Switzerland Alps. This study aimed at exploring the fungal communities present on rinds of cheese produced and matured in Southern Switzerland. We used classical techniques such as dilution series, culturing and macro- and microscopical morphology, matrix-assisted laser desorption/ionization–time of flight (MALDI-TOF) mass spectrometry, and sequencing, as well as metabarcoding targeting the ITS and β-tubulin gene regions, to characterize the fungal communities present of cheese rinds collected in five ripening cellars. Results: Isolation by serial dilution yielded 201 isolates, of which 39 were yeasts and 162 filamentous fungi. Mucor and Penicillium were the dominant genera. Mucor racemosus, M. lanceolatus, P. camemberti, and P. chrysogenum/rubens were the most frequent species. All but two yeast isolates were identified as Debaryomyces hansenii. Overall, metabarcoding detected 80 fungal species, with Mucor spp. and Penicilliumspp. being the dominant taxa, as opposed to only 9 species recovered by serial dilutions. Culture-dependent and independent methods produced similar results in terms of dominant taxa and similarity of the fungal communities in the five cellars, metabarcoding, however, providing more detailed information. Conclusions: Our study has shown that the mycobiota on the rinds of alpine cheese is a complex community defined by different parameters, including temperature, relative humidity, and type of cheese, as well as microenvironmental and possibly geographic factors.
The Swiss Alpine environments are poorly described from a microbiological perspective. Near the Greina plateau in the Camadra valley in Ticino (southern Swiss Alps), a green-turquoise-coloured water spring streams off the mountain cliffs. Geochemical profiling revealed naturally elevated concentrations of heavy metals such as copper, lithium, zinc and cadmium, which are highly unusual for the geomorphology of the region. Of particular interest, was the presence of a thick biofilm, that was revealed by microscopic analysis to be mainly composed of Cyanobacteria. A metagenome was further assembled to detail the genes found in this environment. A multitude of genes for resistance/tolerance to high heavy metal concentrations were indeed found, such as, various transport systems, and genes involved in the synthesis of extracellular polymeric substances (EPS). EPS have been evoked as a central component in photosynthetic environments rich in heavy metals, for their ability to drive the sequestration of toxic, positively-charged metal ions under high regimes of cyanobacteria-driven photosynthesis. The results of this study provide a geochemical and microbiological description of this unusual environment in the southern Swiss Alps, the role of cyanobacterial photosynthesis in metal resistance, and the potential role of such microbial community in bioremediation of metal-contaminated environments.
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